(Not so) mysterious ways

By Lisa Rummler

October 2009 - When it comes to the sights and sounds of a concert, the latter definitely trumps the former. Ultimately, the music draws in fans, not the cool lighting, an impressive venue or even the lead singer's looks.

But that's not to say a nonmusical element, including a state-of-the-art stage, can't add something to the overall concert experience.

That's the case with U2's 360 Tour. Fans flock to hear Bono and the band, who work the crowd from a 254-ton stage known as "the claw."

Created by set designer Willy Williams and stage architect Mark Fisher, the claw is a steel stage construction that stands on four legs and stretches 99 feet tall.
The design enables concertgoers to have an unobstructed view of the band, no matter where they're standing in relation to the stage.

Elevation
Having designed and built the stage for U2's PopMart Tour in 1997 and 1998, Stageco, Tildonk, Belgium, was drafted for the construction of the claw.

The 360 Tour presented unique challenges, though. Specifically, three stages had to be built because there's only a short amount of time between performances, and it takes seven to eight days to assemble and dismantle each stage.

According to a press release, "[They] are used following the 'leapfrogging principle': One is used for the show [while] the second is already being built at the next location and the third is being dismantled at the previous location. The challenge for Stageco was, therefore, how to assemble and dismantle the massive 254-ton construction each time."

Along with the stage itself, a 66-ton video screen and the light and sound system have to be put up and taken down at the end of every concert.
According to the press release, "Chain hoists and winches are normally used for stages, with the support of relatively light mobile cranes where required. However, the load in this project was so great that a different solution was called for."

Carrying the load
To find a suitable solution, Stageco partnered with Enerpac, Milwaukee, a division of Actuant Inc., Butler, Wis. Enerpac is a producer of high-force tools and equipment used in industrial markets.

According to the press release, "The requirement was that the system had to be more or less plug-and-play--a ready-to-use hydraulic unit was required that would only need to be connected to the electricity supply and the operating computer. Together, the two companies came up with a solution [that] incorporated Enerpac's custom-designed Synchronous Lift System to use high-pressure hydraulics for the first time ever for such heavy loads."

The complete hoisting system for each of the three stages is made up of 16 lifting cylinders, 16 locking cylinders and four hydraulic units.
Each lifting cylinder has an applied pulling force of 22 tons and a 24-inch stroke, and all of them have a pressure transducer, a built-in stroke sensor and two proximity switches.

All of the 0.6-ton low-pressure locking cylinders have a stroke of 10 inches. Like the lifting cylinders, each has two proximity sensors.
According to the press release, "The steel stage construction consists of a central block, which rests upon four legs, each made up of six sections. The central block is gradually lifted off the ground in 38 steps, and a section is added to each of the four legs after every 6 or 7 seconds."

Here to stay
Although U2's 360 Tour is slated to wrap up in late October, the band will more than likely tour again. And even if the band doesn't hit the road anytime soon, Stageco plans to use the current stage innovations for future concerts.

According to the press release, ÒIt is clear that shows will continue to get bigger and better in the entertainment world. Since Stageco now has this technology in-house, set designers will also have much more freedom, and it will be possible to build spectacular stages at many more locations." MM